This invention relates to a color-stabilized dentifrice composition comprising a cinnamic aldehyde or citral flavorant which is subject to discoloration/yellowing upon aging, and propylene glycol and/or dipropylene glycol which significantly reduces and/or prevents discoloration, and maintaining the pH of said composition below 8.5 and preferably at a slightly alkaline to acid pH. The dentifrice vehicle may be aqueous or anhydrous.
The prior art is replete with dental formulations comprising the combination of a cinnamic aldehyde or citral flavorant and propylene glycol or dipropylene glycol as shown in U.S. Pat. Nos. 3,867,557 and 3,928,560 wherein oral compositions containing 0.0001-20% paramethoxycinnamaldehyde flavoring agent is dissolved in 100 parts propylene glycol; U.S. Pat. No. 4,132,771 and U.S. Pat. No. 4,187,287, wherein a two-tone flavored dentifrice containing cinnamon flavor is in a propylene glycol vehicle; U.S. Pat. No. 4,242,323 wherein a plaque inhibiting oral composition containing cinnamon oil flavorant also utilizes propylene glycol as the liquid vehicle; and U.S. Pat. No. 3,864,472 relating to a clear lemon-flavored mouthwash containing lemon oil, cinnamic aldehyde and glycerine or propylene glycol. U.S. Pat. No. 4,001,438 also discloses flavor formulations comprising citral and/or cinnamic aldehyde as a component in a physically entrapped flavor composition which is admixed with a non-confined flavor oil, a suspending agent and preferably a small amount (0.5%) of propylene glycol which improves product stability (column 6 lines 32-33), useful in oral compositions. However, there is no recognition in this group of patents of the discoloration or yellowing problem due to aging associated with the use of the cinnamic aldehyde flavorant. These patents relate to different aspects in dentifrice formulations. The disclosure of the combination of cinnamic aldehyde flavorant and propylene glycol is incidental to a general discussion of flavorants and typical humectants.
The prior art also recognizes the fading and/or deterioration of flavors as shown in U.S. Pat. No. 3,957,964 wherein the flavoring material, which includes oil of cinnamon or orange, is encapsulated and kept separate from the dentifrice base (which may include propylene glycol) during storage until released when the dentifrice is used, thereby providing a more stable and fresher tasting flavored dentifrice. However, there is no mention in aforesaid patent of the stabilization of the cinnamic aldehyde or citral flavor with propylene glycol or dipropylene glycol.
U.S. Pat. No. 2,184,526 also recognizes the instability against oxidation by air of p-isopropyl-.alpha.-methylhydrocinnamic aldehyde as a perfume ingredient, wherein the aldehyde is converted into the corresponding acid, thereby destroying the aldehyde odor. The addition of alcohols of the aromatic or terpene series stabilizes the aldehyde against air oxidation, by converting the aldehyde into a hemi-acetal of said alcohol, said hemi-acetal functioning as the perfume material.
None of the above cited art discloses the use of propylene glycol or dipropylene glycol in excess of 5% by weight, in a dentifrice, free of oxidizing agents and maintained at an acid or neutral pH, containing the cinnamic aldehyde or citral flavor, to reduce discoloration of said flavorant upon aging.